1. Field of the Invention
The present invention relates to a digital photographic device that is configured by a camera module and a host module, and particularly, the invention relates to the structure for effectively exchanging the control data between the host module and the camera module and the structure for conducting a hardware test and a software test of the camera module.
2. Description of the Related Art
In recent years, there are many occasions that a camera is incorporated in a portable information device such as a cellular phone and a PDA. In such a camera-equipped cellular phone, a camera portion is frequently manufactured as an independent camera module although this camera-equipped cellular phone has a chassis covering the entire device and the camera portion is barely visible, because by making the camera portion into a module, the same module can be easily combined to various different cellular phone and PDA. In addition, since a mass production can be expected, reduction of a manufacturing cost can be also expected. Accordingly, it can be understood that such a camera-equipped information device is configured by a host module controlling a telephone function and a PDA function and a camera module controlling a camera function and two modules are connected each other by an interface. The camera module is provided with an image pickup device of converting a light into an electronic signal, a LED lighting, and an image data construction part of constructing the image data that can be displayed by a computer from the output signal of the image pickup device.
In such a camera-equipped information device, it is common that photographing is carried out by using a user interface provided to the host module, so that the host module normally controls the camera function of the camera module. As such a control method, two methods are conceivable.
At first, according to a first method, the IC (the host IC) of the host module directly controls each configuration device of the camera module. In other words, the host IC may directly control timing of data collection by an image pickup device of the camera module, various parameters relevant to the image processing of the image pickup data, and on and off of the LED light or the like. Such a control is carried out in the case that a processing apparatus provided to the host IC is mounted on the IC of the camera module (the camera IC) and this processing apparatus designates an address of a register for controlling that is connected to the image pickup device and directly outputs a control parameter. In the case of the first method, since the control of the camera IC is carried out when the processing apparatus of the host IC designates the address of the register for controlling and outputs the control parameter, the software of the host IC is necessarily changed when a register map of the camera IC is changed or a control parameter is changed in the middle of development. control of the camera IC is carried out when the processing apparatus of the host IC designates the address of the resistor for controlling and outputs the control parameter, the software of the host IC is necessarily changed when a resister map of the camera IC is changed or a control parameter is changed in the middle of development.
According to a second method, the camera IC itself may directly control each configuration device in such a manner that the camera IC is also provided with the processing apparatus composed of the CUP or software, the host IC transmits a message-based command to the camera IC, and the camera IC interprets this message command. For example, if the host IC transmits a message command of “Start photographing” to the camera IC, the camera IC prepares a control parameter of the image pickup device that is necessary for “Start photographing” by its own processing apparatus and outputs the compliant control parameter to a register for control of the image pickup device.
In the case of the second method, the processing apparatus of the host IC cannot access the register for control of the camera IC. In other words, it is very difficult to check the state of the register for control of the camera IC from the external region. Therefore, it is difficult for the camera IC to appropriately interpret the message command of the host IC and check if the register for control is suitably set or not.
In such a case, as a method of examining the state of the register for control, it is conceivable to use a JTAG. The JTAG is a board test method that is standardized in 1990 as an IEEE 1149.1. The IC of supporting the JTAG is provided with a dedicated signal line for inputting and outputting a message command for testing and a result of processing this message command and the external computer may test the IC through this signal line. Accordingly, the camera IC can check the value of the register for control if the camera IC complies with the JTAG. However, in the case of using the JTAG, the camera IC must have a circuit for the JTAG test and an input and output unit and this leads to increase of the cost.